"Un colon anglicisé" works on a number of levels. Obviously, it can refer to the use of the colon as a punctuation mark in English.
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"Colon" is also French for a colonist or settler, so the singer is suggesting that he's an Anglicized colonizer of Québec.
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"Colon" is also Québec slang for an idiot, or someone uncultured and obnoxious.
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Finally, as in English, "colon" is also a pun on "côlon," referring to the digestive organ.
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Obviously, the point of the song is to poke fun at the use of Anglicisms in Canadian French.